Geothermal power plants utilizing a geothermal fluid source are generally known. The simplest to use and the most economical are the dry steam and steam dominated hydrothermal resources which are similar to conventional power plants. Others use geothermal sources of low to moderate temperature with chemically benign fluid as a heat source. These plants are also relatively simple in design and operation, but operate at low thermal efficiencies due to the temperature range typical of the geothermal sources.
Another source of heat which enables a higher thermal efficiency is a high-temperature hyper-saline brine from a deeper geothermal source having a high concentration of gases and dissolved fluids. Such a source enables a higher thermal efficiency, but is more difficult to handle because of the chemistry of the geothermal fluid. These high-temperature geothermal sources are often vertically superimposed below a lower, more chemically-benign geothermal source, with the deeper, higher-temperature geothermal resource providing heat to the shallower, lower-temperature geothermal source.
Typically, plants designed to utilize the high-temperature, hyper-saline source required double or triple flash high efficiency steam turbines, which produced precipitated solids requiring disposal in hazardous material landfills. Another approach was to use a flash-crystallizer/reactor clarifier (FCRC) system, where clean steam is generated in a train of separators and flash vessels, with the separated brine seeded with material that induces precipitation in the brine rather than on the surfaces of the vessels and piping. The precipitated matter in the brine is eventually allowed to settle in a reactor-clarifier vessel, with the clarified liquid pumped to a secondary clarifier and sent to reinjection wells. Still another solution is to reduce or delay precipitation by adding acid to the brine to lower its pH. While this helps prevent precipitation in the system, adding acid requires the use of corrosion-resistant materials, and may require additional chemical treatment to restore the brine to its original chemistry prior to reinjection.
Therefore, there remains a need to provide a new and improved method of and apparatus for producing power using high-temperature, hyper-saline brine without requiring complex designs or expensive waste treatment.